Method of Enhancing Ultrasound Visibility of Hyperechoic Materials

ABSTRACT

A permanent or temporary marker is embedded within a hydrogel plug used in a biopsy procedure to indicate the location of a suspicious lesion so that the marker may be found in a subsequent surgical procedure. A combination of at least one permanent and at least one temporary marker may be used. Inserts of differing sizes and shapes may also be placed into the hydrogel plugs during their manufacturing process and removed from the plugs after the plugs have cured so that air-filled cavities are left in the plug. These cavities are temporary but may be used to augment location of a permanent marker.

CROSS-REFERENCE TO RELATED DISCLOSURES

This disclosure is a continuation-in-part of U.S. patent applicationSer. No. 11/277,721, filed Mar. 28, 2006, by the same inventors andhaving the same title. That disclosure is hereby incorporated byreference in its entirety into this disclosure.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates, generally, to a method for improving thevisibility of a hyperechoic marker or markers under ultrasound. Suchmarkers are used to indicate the location of a tumor or lesion so that aprocedure to remove such lesion or tumor may be performed weeks ormonths after the marker has been implanted. More particularly, itrelates to markers that incorporate hydrogels to enhance the visibilityof the markers with imaging techniques such as ultrasound and to methodsfor making such markers.

2. Description of the Prior Art

A permanent metal or hard plastic, such as a permanent, bio-compatibleplastic such as polyethylene, or temporary, bioabsorbable, biocompatibleplastic such as PGA/PLA, or other suitable marker must be left at abiopsy site at the completion of a biopsy if the site is to be locatedagain in the future. Biodegradable markers are not permanent andtherefore cannot be relied upon if a biopsy site is to be re-located ata time remote from the time of the biopsy. However, there areapplications where a temporary, biodegradable marker may have utility,either when used alone, in combination with other temporary markers, orin combination with one or more permanent markers. Suture andcollagen-based markers are not suitable as markers because they arehyperechoic, i.e., difficult to see under ultrasound because suchmaterials are easily confused with other shadowing normal structures inthe body such as fibrous tissue, fatty tissue, ducts in breast tissue,and the like, for example. Such tissue provides a background clutterthat masks the presence of a marker made of metal, hard plastic, orother hyperechoic material.

Water, unlike metal, hard plastic, and other hyperechoic materials, ishypoechoic, i.e., easy to see under imaging techniques such asultrasound. Therefore it would be advantageous if a marker made of ahyperechoic material such as metal or hard plastic could be surroundedby an easily seen quantity of water.

However, the art includes no means for surrounding a hyperechoic markerwith water at a biopsy site.

There is a need, then, for a permanent marker that is surrounded bywater after it has been positioned at a biopsy site.

There is also a need, however, for a non-permanent, i.e., temporarymarker that is surrounded by a hypoechoic material such as water at abiopsy site.

Moreover, there is a need for both permanent and temporary markersformed of hyperechoic materials, or temporary hyperechoic markers alone,surrounded by a hypoechoic material.

A need also exists for a hydrogel manufacturing process that produces acured and dehydrated plug or marker that contracts in length andincreases in diameter upon being hydrated.

There is also a need for a hydrogel manufacturing process that producesa cured and dehydrated plug or marker that contracts in width andincreases in length and height upon being hydrated.

There is also a further need for a hydrogel manufacturing process thatproduces a cured and dehydrated plug or marker that contracts radiallyand increases in length upon being hydrated

However, in view of the prior art taken as a whole at the time thepresent invention was made, it was not obvious to those of ordinaryskill how the identified needs could be fulfilled.

SUMMARY OF THE INVENTION

The long-standing but heretofore unfulfilled need for a dehydratedmarker that encapsulates a permanent hyperechoic marker, a temporaryhyperechoic marker, or permanent and temporary hyperechoic markers incombination with one another, and that facilitates imaging of saidhyperechoic markers is met by this new, useful, and non-obviousinvention.

The long-standing but heretofore unfulfilled need for a dehydratedmarker that contracts in length and increases in diameter, contracts inwidth and increases in length, or radially contracts and increases inlength when hydrated, and a method for making such a marker, is also metby this invention.

Hydrogel, in order to be effective in the application of this invention,should contain about eighty to ninety percent (80%-90%) water. Hydrogelscan contain higher or lower percentages of water but the range of eightyto ninety percent is believed to be optimal for the purposes of thisinvention but this invention is not limited to that particular range.Forming a biopsy marker from a hydrogel therefore provides a way tocontain water so that it does not flow. It would be advantageous toembed a permanent hyperechoic marker within a cured and dehydratedhydrogel marker or plug. It would also be advantageous to embed atemporary hyperechoic marker, or a combination of permanent andtemporary hyperechoic markers within a cured and dehydrated marker orplug. The plug would become hydrated by natural body moisture afterbeing positioned at a biopsy site, thereby surrounding the permanentmarker with water. The water would be easily seen under ultrasound andtherefore the marker it surrounds would be easy to see.

The permanent marker may be positioned in the center of the hydrogel oroff-center with respect thereto. A temporary marker, or a combination ofpermanent and temporary markers, may also be so positioned. The markersmay even be positioned external to the hydrogel. In the latter case, arecord may be made to the effect that the marker or markers will befound at the six o'clock position relative to the hydrogel, or the like.

The novel hydrogel polymer has a permanent or temporary marker, or acombination of permanent and temporary markers formed of metal, hardplastic, or other hyperechoic material embedded within the polymer. Thehydration of the polymer by the natural moisture of the tissuesurrounding it causes expansion of the polymer and thus minimizes therisk of migration. The growing hydrogel centers itself in the biopsycavity as it grows.

The novel hydrogel composition does not include PGA/PLA. It ispreferably peg-based and has advantages in imaging. Specifically, theplug is mostly water when hydrated. This provides a significantadvantage because water is easily visible when ultrasound is employed asaforesaid.

The novel marker has two (2) imaging stages. The plug is solid and drywhen it is deployed initially to mark the cavity created by a biopsyprocedure.

The solid, dry plug is seen as a shadowing, hyperechoic, linear objectwith posterior acoustic shadowing on ultrasound.

However, as the hydrogel expands, due to naturally-present moisture fromthe surrounding tissue, the hydration enables increasing sound throughtransmission, appears more and more hypoechoic, and is easy to visualizeon follow up ultrasound studies. The hydrogel, when hydrated, appearsblack in color, centers itself in the biopsy or other cavity as itgrows, and frames the permanent, temporary, or combination of permanentand temporary markers.

The polymer plug is molded and cured into different shapes to avoidconfusion with normal breast structures such as ducts. The shapes can berod-like, spiral, round, toroidal, rectangular, string of pearls or anyother predetermined geometrical configuration that does not have anappearance that resembles a naturally-occurring feature.

The hypoechoic nature of the hydrated plug enables ultrasound visibilityof the permanent, temporary or combination of permanent and temporarymarkers within the hydrogel hydrated plug because the permanent,temporary, or permanent/temporary combination marker is outlined as aspecular reflector within a hypoechoic hydrated marker plug having awater-like nonreflective substrate.

Water is the most easily visualized substrate under ultrasound. Thepermanent, temporary, or combination of permanent and temporary markersof this invention can have any shape that are not easily confused with anatural shape as mentioned above and it can be made of any permanentmetallic-like or hard plastic material. Helical shapes having a hollowinterior is a preferred shape because it allows the polymer to betterretain the marker within.

Permanent and temporary markers may also be augmented by cavities formedin the hypoechoic material that encapsulates the markers. Such cavitiesare hypoechoic and thus serve to further indicate the location of themarker. The size and shape of the cavity or cavities is determined atthe time the plug is manufactured. Specifically, the cavity or cavitiesare formed by inserts of differing shapes and sizes that are positionedinside the hydrogel during the curing process. The inserts are removedfrom the hydrogel after the hydrogel has cured, leaving the cavity orcavities in the hydrogel. The cavities are air-filled and thus reflectunder ultrasound imaging in a way that differs from the reflection ofthe hydrogel. The cavities are not permanent because the air graduallyescapes. The length of time required for the air to escape depends uponthe size of the cavity, the shape of the cavity and whether or not thecavity is completely encapsulated or is in communication with thesurface of the hydrogel.

An elongate suture may also have a first end embedded in a hydrogel plugduring the curing and hydration process so that a second end of thesuture may be positioned externally of a patient's body after a biopsyprocedure.

The permanent, temporary, or combination permanent and temporarymetallic or hard plastic markers may have a rod shape, a cylindricalshape, a coil shape, or other suitable shape. The coil configurationallows hydrogel to cure inside the core of the coil and between theloops of the coil to achieve a complete and smooth coverage of thehyperechoic marker by the hypoechoic hydrogel.

The novel marker or markers have several medical applications for softtissue implants with a controlled RE/LC ratio. For example, it may beused as a soft tissue or void filler in cosmetic applications. Aphysician would start with a small size implant that expands in time tofill a cavity in a radial direction only without any longitudinalexpansion.

Hydrogel implants post hydration are softer than most conventionalimplants and can take different shapes in filling soft tissue cavities.Expansion in the length direction may need to be controlled to maintainthe desired shape.

There are also applications that require a higher than usual expansionrate, and there are applications where higher expansion rates are neededfor small dehydrated implants in one direction only while contraction orshrinkage occurs in a different direction.

A primary advantage of the novel markers is that they provide a metal,hard plastic, or other permanent, temporary or combination marker thatis easy to see under imaging because it is surrounded by water due tothe hydration of the hydrogel within which it is embedded.

These and other advantages will become apparent as this disclosureproceeds. The invention includes the features of construction,arrangement of parts, and combination of elements set forth herein, andthe scope of the invention is set forth in the claims appended hereto.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the nature and objects of the invention,reference should be made to the following detailed description, taken inconnection with the accompanying drawings, in which:

FIG. 1A is a front elevational view of a first embodiment of a hydrogelplug in a position of repose having a plurality of temporary,biodegradable markers embedded therewithin;

FIG. 1B is an end elevational view of the embodiment depicted in FIG.1A;

FIG. 2A is a front elevational view of a second embodiment of a hydrogelplug in repose having a combination of temporary and permanent markers;

FIG. 2B is an end elevational view of the embodiment depicted in FIG.2A;

FIG. 3 is a front elevational view of a hydrogel plug having a pluralityof large, round cavities formed therein;

FIG. 4 is a front elevational view of a hydrogel plug having a pluralityof small, round cavities formed therein;

FIG. 5 is a front elevational view of a hydrogel plug having acompletely encapsulated sinusoidal cavity formed therein;

FIG. 6 is a view like that of FIG. 5 but where the opposite ends of thesinusoidal cavity are in open communication with a surfaced of thehydrogel plug; and

FIG. 7 is a front elevational view of a hydrogel plug having a first endof an elongate suture embedded therein so that a second end of saidsuture may be positioned externally of the patient when the biopsyprocedure is completed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIGS. 1A and 1B, it will there be seen that a firstillustrative embodiment of the invention is denoted as a whole by thereference numeral 10.

Hydrogel plug 10 includes a plurality of temporary markers, collectivelydenoted 12, embedded within a hydrogel material 14 having, in this firstembodiment, a shape designed to inhibit migration of the plug withintissue. The FIG. 1A configuration is the “in repose” configuration ofplug 10. Markers 12 may be formed of metal, hard plastic, or otherpermanent material but the depicted markers 12 are formed of atemporary, biodegradable materials.

FIGS. 1A and 1B depict multiple temporary markers 12 of differing sizesand shapes just to illustrate that the markers may be provided in aninfinite variety of geometrical configurations. Thus it should beunderstood that a single temporary marker 12 is within the scope of thisinvention. Accordingly, the novel method of this invention includes thestep of selecting at least one temporary, biodegradable marker from agroup of markers that includes permanent and temporary, biodegradablemarkers.

The preferred temporary, biodegradable marker is a biodegradable moldedpolymer made of PGA/PLA or other suitable biodegradable materials thatare compatible and otherwise suitable for use in human tissue.

In the alternative, as depicted in FIGS. 2A and 2B, one or morepermanent markers 16 may be used in combination with one or moretemporary markers 12. It should be noted that the marker or markers maybe embedded in the center of the hydrogel 14 or at any off centerlocation. It may even be positioned outside the hydrogel if a record ismade recording the location of the marker relative to the hydrogel.

The embodiment of FIG. 3 includes a permanent marker and plurality oflarge, round air-filled cavities, collectively denoted 18. Theseair-filled cavities reflect ultrasound in a way that is distinguishablefrom hydrogel reflection and thus said cavities serve to help point outthe location of the permanent marker. The cavities may also be providedin hydrogel plugs having no permanent marker or markers embeddedtherein. One or more of the cavities could also be in open communicationwith the surface of the hydrogel plug. Moreover, the cavities need nothave a common size or shape and they may be of any size and anypredetermined geometrical configuration. The use of a single cavity isalso within the scope of this invention.

FIG. 4 provides an example where the cavities 18 are smaller in size andgreater in number than the embodiment of FIG. 3.

The embodiment of FIG. 5 includes a fully embedded sinusoidal cavity 20and the embodiment of FIG. 6 includes a sinusoidal cavity that is inopen communication with the surface of the hydrogel plug at its oppositeends 20 a, 20 b. Another drawing could be provided to depict only oneend of the sinusoidal cavity in such open communication and stillfurther drawings could depict a maximum or minimum amplitude of cavity20 in such open communication but such drawings are not provided toconserve resources.

The embodiment of FIG. 7 depicts elongate suture 22 having a first end22 a embedded in a hydrogel plug so that second end 22 b thereof may bepositioned externally of a patient's body after a biopsy procedure hasbeen completed.

This invention is not limited to any particular shape. Hydrogel material14 may be formed into any shape that inhibits migration.

Marker 12 could also be positioned in the interior of a balloon or otherbladder and said balloon or bladder could be filled with water. Althoughthis may not be a practical way of identifying the location of apermanent or temporary marker, or combination thereof, it would workbecause water is hypoechoic and such an apparatus would thereforeidentify the location of a hyperechoic marker.

The applications of this invention are not limited to permanent,temporary or combination markers encapsulated in hydrogel for use inbiopsy procedures. The same method may be used to facilitate detectionof any metal, hard plastic, or other hyperechoic structures in the bodysuch as vascular stents, surgical staples, embolization coils, radiationseed, aneurysm clips, electrode stimulation wires, prosthetic valves,stent grafts, biliary stents, drug delivery metal containers ordispensers, and the like.

It will thus be seen that the objects set forth above, and those madeapparent from the foregoing description, are efficiently attained andsince certain changes may be made in the above construction withoutdeparting from the scope of the invention, it is intended that allmatters contained in the foregoing description or shown in theaccompanying drawings shall be interpreted as illustrative and not in alimiting sense.

It is also to be understood that the following claims are intended tocover all of the generic and specific features of the invention hereindescribed, and all statements of the scope of the invention that, as amatter of language, might be said to fall therebetween.

Now that the invention has been described,

1. A method for facilitating ultrasound viewing of a hyperechoicmaterial disposed within tissue, comprising the steps of: selecting atleast one hyperechoic material from a group of hyperechoic materialsincluding permanent and temporary, biodegradable hyperechoic materials;encapsulating said at least one hyperechoic material within a hypoechoicmaterial so that the hypoechoic material surrounds the at least onehyperechoic material and therefore identifies the location of the atleast one hyperechoic material.
 2. The method of claim 1, furthercomprising the step of: employing a hydrogel as said hypoechoicmaterial.
 3. The method of claim 2, further comprising the steps of:inserting the at least one hyperechoic material within the hydrogel whenthe hydrogel is in a non-hydrated state; and inserting the hydrogel intotissue so that natural moisture of the body hydrates said hydrogel;whereby the hydrated hydrogel is easily seen under ultrasound; andwhereby the position of the at least one hyperechoic material isindicated by the hydrated hydrogel.
 4. A method for facilitatingultrasound viewing of a hyperechoic material disposed within tissue,comprising the steps of: positioning at least one insert having apredetermined size and shape into a hydrogel plug when said hydrogelplug is manufactured; removing said at least one insert from saidhydrogel plug after said hydrogel plug has been manufactured; whereby atleast one air-filled cavity is formed in said hydrogel plug.
 5. Themethod of claim 4, further comprising the step of: positioning said atleast one insert within said hydrogel plug so that said at least oneinsert is wholly embedded with the hydrogel plug.
 6. The method of claim4, further comprising the step of: positioning said at least one insertwithin said hydrogel plug so that said at least one insert is in opencommunication with an external surface of the hydrogel plug.
 7. A methodfor facilitating ultrasound viewing of a hyperechoic material disposedwithin tissue, comprising the step of: selecting at least onehyperechoic material from a group of hyperechoic materials includingpermanent and temporary, biodegradable materials; positioning said atleast one hyperechoic material adjacent a hypoechoic material so thatthe hypoechoic material is near the at least one hyperechoic materialand therefore identifies the location of the at least one hyperechoicmaterial.